CN104113056A - Method for optimizing low-voltage current-limiting control parameters - Google Patents

Abstract

The invention discloses a method for optimizing low-voltage current-limiting control parameters. The method design an optimization objective function giving consideration to an active transmission characteristic and a reactive consumption characteristic of a converter station, and a maximum voltage threshold value VD_H, a minimum voltage threshold value VD_L and a minimum current limit value ID_L of a low-voltage current-limiting module are selected as optimization variables; and a custom function of electromagnetic transient time-domain simulation software embeds the optimization target function and the optimization method in a simulation program, thereby realizing efficient optimization of the low-voltage current-limiting parameters.

Description

A kind of optimization method of low voltage limit flow control parameter

Technical field

The present invention relates to a kind of optimization method of HVDC (High Voltage Direct Current) transmission system low voltage limit flow control parameter, belong to electric power system control running protection technical field.

Background technology

The current limiting low-voltage of HVDC (High Voltage Direct Current) transmission system is controlled and is referred to and direct current is limited exchanging when commutation voltage or direct voltage are reduced to certain value, by restriction direct current, suppress on the one hand the demand of converter to reactive power consumption, thereby increase on the other hand leading Trigger Angle β and increase extinguish angle γ, with this, reduce the possibility that follow-up commutation failure occurs.Although if cross by force and can reduce converter to idle demand for the restriction of direct current, will hinder converter active power will be transmitted to resume speed.Experts and scholars often only studied how reducing in converter reactive requirement or direct current transmission recovery characteristics in the past, from the two qualitative optimizations in aspect, did not propose reliable research method.How to solve converter reactive power consumption and meritorious transmission coordination optimization problem rises up into research.This patent proposes significantly to reduce in ac and dc systems fault and between convalescence Inverter Station the reactive requirement of AC system and meritorious fast quick-recovery is proposed to Mathematical Modeling quantization scheme in converter current limiting low-voltage controlling unit, retain typical current limiting low-voltage simultaneously and controlled the characteristic that can stablize alternating voltage, be conducive to reduce the possibility of follow-up commutation failure.

Current limiting low-voltage control characteristic is mainly subject to four parameters (ID_L, ID_H, VD_L, VD_H) impact, and its setting value is determined according to operation characteristic under a series of disturbances and low pressure.Under system failure operation, the parameter of current limiting low-voltage device is to voltage, the meritorious transmission of angle stability, reactive requirement and flow to very crucial.Conventionally ID_H numerical value is constant is 1.0, therefore can comprise for the parameter of optimization tri-of ID_L, VD_L and VD_H.With the transformation of alternating current-direct current primary system is compared, to the optimization of current limiting low-voltage parameter, only need pay very little cost and can produce good effect to the recovery of direct current system.Yet the optimization means of current limiting low-voltage parameter is limited to the method that examination is gathered more at present, depends on engineering experience, and efficiency is lower, classical current limiting low-voltage control characteristic broken line is as shown in curve before changing in Fig. 3.

Summary of the invention

For overcoming the deficiencies in the prior art, the present invention proposes a kind of parameter intelligent optimization method for HVDC (High Voltage Direct Current) transmission system mesolow Current limited Control; After its object is to solve DC transmission system fault, converter suppresses reactive requirement and accelerates the coordination optimization problem between meritorious recovery; Optimize low voltage limit flow control parameter, intelligent search optimized operation point, makes consumed idle peak value as far as possible little, and meritorious transmission simultaneously recovers fast as far as possible, improves the runnability in direct current system transient process.

The technical scheme that the present invention takes is:

An optimization method for low voltage limit flow control parameter, it comprises the following steps:

Step 1, foundation take into account the optimization aim function of the meritorious restorability of direct current and converter reactive power consumption size, and described optimization aim function is:

minf(x)＝(ω _pΔE _loss+ω _qΔQ _peak) (1)

Wherein: minf (x) is optimization aim minimum of a function value, Δ E _loss, Δ Q _peakbe respectively the meritorious restorability of direct current and converter reactive power consumption size, ω _pand ω _qbe respectively Δ E _loss, Δ Q _peakweights, and ω _p+ ω _q=1.0;

Step 2, determine the control parameter of optimizable current limiting low-voltage, described control parameter comprises ceiling voltage threshold value VD_H, minimum voltage threshold value VD_L and tri-variablees of minimum current limit value ID_L, according to the number range of described three variablees, forms optimizing feasible zone;

Step 3, by electro-magnetic transient time-domain-simulation program, embed optimized algorithm, obtain the optimum low voltage limit flow control parameter in described optimizing feasible zone;

Step 4, by electromagnetic transient simulation, contrast the dynamic response under low voltage limit flow control parameter initial value and optimal control parameter, the feasibility of checking optimum results;

Wherein: described step 3 comprises:

Step 31, utilize electromagnetic transient simulation program to set up the computation model of optimization aim function and optimized algorithm, and carry out initialization;

Step 32, by described computation model, provided one group of given control parameter of current limiting low-voltage, according to described given control parameter, the electromagnetic transient simulation that carries out electric network calculates, and obtains initial optimization target function value f ₁;

Step 33, employing optimized algorithm successively produce new control parameter, again carry out electromagnetic transient simulation calculating, obtain optimization aim function calculated value f _j, when:

$\left\{\begin{array}{c}|f_j-f_{-1}|\&le;\mathrm{\&epsiv;}\\ f_j<\min \left\{f_i\right\}\\ i\&Element;(0,j),i\&Element;Z\end{array}\right.---\left(2\right)$

Time, think and calculate convergence, this optimization aim function calculated value f _jcorresponding control parameter is optimal control parameter, otherwise, execution step 34;

Step 34, judgement are optimized number of times and whether are reached maximum simulation times, if so, choose optimization aim function calculated value f _jwith initial optimization target function value f ₁a corresponding control parameter of middle minimum is as optimal control parameter, otherwise continuation performs step 33.

Δ E in described step 1 _losscomputational methods be:

$\left\{\begin{array}{c}{\mathrm{\&Delta;E}}_{\mathrm{loss}}=E_{\mathrm{loss}}/E_{\mathrm{loss}0}-1.0\\ E_{\mathrm{loss}}={\&Integral;}_{t0}^{t1}(P_s-P\left(t\right))\mathrm{dt}\\ E_{\mathrm{loss}0}={\&Integral;}_{t0}^{t1}(P_s-P_0\left(t\right))\mathrm{dt}\end{array}\right.---\left(3\right)$

Wherein, P _sfor the active power that direct current under steady state situations is carried, P ₀be respectively under same fault condition with P, direct current system adopts low voltage limit flow control parameter initial value and optimal control parameter to calculate separately the active power of gained, and t0 is the fault clearance moment, and t1 is that direct current active power returns to P _smoment of 90%.

Described Δ Q _peakcomputational methods be:

ΔQ _peak＝Q _peak/Q _peak0-1.0 (4)

Wherein, Q _peak0and Q _peakbe respectively under same fault condition, direct current system adopts low voltage limit flow control parameter initial value and optimal control parameter to calculate separately the idle numerical value of maximum that between convalescence of gained, inverter consumes.

The current limiting low-voltage of described low voltage limit flow control parameter initial value when not being optimized controlled parameter value.

According to engineering experience, the number range of described three variablees is limited:

$\left\{\begin{array}{c}0.4\&le;\mathrm{VD}\_H\&le;0.9\\ 0.1\&le;\mathrm{VD}\_L\&le;0.6\\ 0.2\&le;\mathrm{ID}\_L\&le;0.5\\ \mathrm{VD}\_H\&GreaterEqual;\mathrm{VD}\_L\end{array}\right.---\left(5\right).$

Described dynamic response comprises the active power of inverter transmission and the reactive power of consumption.

Described optimized algorithm is genetic algorithm.

The present invention compared with prior art, its beneficial effect is: it sets up the computation model of optimization aim function and optimized algorithm by electromagnetic transient simulation program, and in optimizing feasible zone, obtain minimum optimization aim function, to optimize low voltage limit flow control parameter, intelligent search optimized operation point, make consumed idle peak value as far as possible little, meritorious transmission simultaneously recovers fast as far as possible, improves the runnability in direct current system transient process.

Accompanying drawing explanation

Fig. 1 is the electromagnetic transient simulation result figure of the active power of inverter transmission and the dynamic response of the reactive power of consumption before and after current limiting low-voltage parameter optimization;

Fig. 2 is the schematic flow sheet of step 3 of the present invention;

Fig. 3 is certain ± 800KV extra-high voltage direct-current control system current limiting low-voltage optimize before and after characteristic fold line comparison diagram.

Embodiment

Below in conjunction with the drawings and specific embodiments, content of the present invention is described in further details.

Embodiment

A current limiting low-voltage Optimization about control parameter method, it comprises the following steps:

The optimization aim of step 1, a reflection DC system fault restorability of design.This index is taken into account the meritorious resume speed of direct current and converter reactive power consumption size.

Step 2, determine and the control parameter of optimizable current limiting low-voltage comprise ceiling voltage threshold value VD_H, minimum voltage threshold value VD_L and tri-variablees of minimum current limit value ID_L, form optimizing feasible zone.

Step 3, design a kind of intelligent optimization method that is adapted to electro-magnetic transient time-domain-simulation program, user can obtain the optimum low voltage limit flow control parameter under set objective by working procedure.

Step 4, by electromagnetic transient simulation, contrast the result before and after optimizing, the feasibility of checking optimum results.If there is unreasonable result, need to return step 2 and revise optimizing feasible zone.

Optimization aim in step 1 has been taken into account the meritorious recovery of direct current and the reactive power consumption of converter, comprising describing the quantitative indices of meritorious restorability and converter reactive power consumption.

Step 11, to design optimization aim function as follows:

Minf (x)=(ω _pΔ E _loss+ ω _qΔ Q _peak) (6) wherein, Δ E _loss, Δ Q _peakas shown in formula (7), (8), ω _eand ω _qdifference Δ E _losswith Δ Q _peakweights, ω _e+ ω _q=1.0.

Step 12, employing index Δ E _lossportray the meritorious restorability of direct current:

$\left\{\begin{array}{c}{\mathrm{\&Delta;E}}_{\mathrm{loss}}=E_{\mathrm{loss}}/E_{\mathrm{loss}0}-1.0\\ E_{\mathrm{loss}}={\&Integral;}_{t0}^{t1}(P_s-P\left(t\right))\mathrm{dt}\\ E_{\mathrm{loss}0}={\&Integral;}_{t0}^{t1}(P_s-P_0\left(t\right))\mathrm{dt}\end{array}\right.---\left(7\right)$

Wherein, P _sfor the active power that direct current under steady state situations is carried, P ₀be respectively under same fault condition with P, direct current system adopts the numerical value after low voltage limit flow control parameter initial value and optimization to calculate separately the active power of gained, and t0 is the fault clearance moment, and t1 is that direct current active power returns to P _smoment of 90%.

Δ Q is portrayed in step 13, employing _peakthe size of converter reactive power consumption:

ΔQ _peak＝Q _peak/Q _peak0-1.0 (8)

Wherein, Q _peak0and Q _peakbe respectively under same fault condition, direct current system adopt low voltage limit flow control parameter initial value and optimize after numerical value calculate separately the idle numerical value of maximum that between convalescence of gained, inverter consumes.

Optimizing feasible zone in step 2 is by ceiling voltage threshold value VD_H, minimum voltage threshold value VD_L and tri-parameter-definitions of minimum current limit value ID_L of current limiting low-voltage, and the number range of these three parameters limits as follows according to engineering experience:

$\left\{\begin{array}{c}0.4\&le;\mathrm{VD}\_H\&le;0.9\\ 0.1\&le;\mathrm{VD}\_L\&le;0.6\\ 0.2\&le;\mathrm{ID}\_L\&le;0.5\\ \mathrm{VD}\_H\&GreaterEqual;\mathrm{VDL}\end{array}\right.---\left(9\right)$

In step 3, in electro-magnetic transient time-domain-simulation program, embed optimized algorithm, please refer to shown in Fig. 2, it specifically comprises:

Step 31, utilize " User Defined " function of electromagnetic transient simulation program (for example PSCAD/EMTDC) to set up the computation model of target function and related optimization (as genetic algorithm), and carry out initialization;

Step 32, by the computation model in step 31, provide one group of current limiting low-voltage and control parameter, the primary data that it is optimized as current limiting low-voltage, according to this primary data, the electromagnetic transient simulation that carries out electric network calculates;

Step 33, according to step 32 electromagnetic transient simulation result calculating target function numerical value, and with last comparison of computational results, suc as formula (10), judge, if the absolute value of the difference of the two is less than, set constant ε, and current iteration calculated value f _jbe less than f _i(wherein, i ∈ (0, j), i is integer), thinks and calculates convergence, last group is controlled parameter and is optimized parameter and shuts down, otherwise (also comprise last result of calculation does not exist and situation about cannot compare) enters step 34.

$\left\{\begin{array}{c}|f_j-f_{j-1}|\&le;\mathrm{\&epsiv;}\\ f_j<\min \left\{f_i\right\}\\ i\&Element;(0,j),i\&Element;Z\end{array}\right.---\left(10\right)$

Step 34, judge whether maximum simulation times that arrive to set.If so, choose one group of minimum current limiting low-voltage parameter of target function f (x) as optimized parameter and shut down; If not, the optimization method in invocation step 31 continues to find next group low voltage limit flow control parameter, and returns to step 32.

The feasibility of step 4 checking optimum results.

By the following examples the present invention is made to further supplementary notes:

Choose PSCAD/EMTDC as electro-magnetic transient time-domain-simulation platform, according to step 1～step 3 of the present invention, to certain ± 800KV extra-high voltage direct-current control system current limiting low-voltage VD_H, VD_L and tri-parameters of ID_L are optimized, and selected ω _p=ω _q=0.5.Three parameter of gained before and after optimizing and corresponding target function numerical value are as following table:

Table 1 is optimized three parameters and the corresponding target function numerical value of front and back

According to step 4 of the present invention, on inversion side change of current bus, three phase short circuit fault is set, earth resistance is 8 Ω, and the duration is 100ms, the active power of simulation comparison inverter transmission and the dynamic response of the reactive power of consumption before and after current limiting low-voltage parameter optimization, as shown in Figure 1.

Although the present invention describes by specific embodiment, it will be appreciated by those skilled in the art that, without departing from the present invention, can also carry out various conversion and be equal to alternative the present invention.In addition, for particular condition or application, can make various modifications to the present invention, and not depart from the scope of the present invention.Therefore, the present invention is not limited to disclosed specific embodiment, and should comprise the whole execution modes that fall within the scope of the claims in the present invention.

Claims (8)

1. an optimization method for low voltage limit flow control parameter, is characterized in that, it comprises the following steps:

Step 1, foundation take into account the optimization aim function of the meritorious restorability of direct current and converter reactive power consumption size, and described optimization aim function is:

minf(x)＝(ω _pΔE _loss+ω _qΔQ _peak) (1)

Wherein: minf (x) is optimization aim minimum of a function value, Δ E _loss, Δ Q _peakbe respectively the meritorious restorability of direct current and converter reactive power consumption size, ω _pand ω _qbe respectively Δ E _loss, Δ Q _peakweights, and ω _p+ ω _q=1.0;

Step 2, determine the control parameter of optimizable current limiting low-voltage, described control parameter comprises ceiling voltage threshold value VD_H, minimum voltage threshold value VD_L and tri-variablees of minimum current limit value ID_L, according to the number range of described three variablees, forms optimizing feasible zone;

Step 3, by electro-magnetic transient time-domain-simulation program, embed optimized algorithm, obtain the optimum low voltage limit flow control parameter in described optimizing feasible zone;

Step 4, by electromagnetic transient simulation, contrast the dynamic response under low voltage limit flow control parameter initial value and optimal control parameter, the feasibility of checking optimum results;

Wherein: described step 3 comprises:

Step 31, utilize electromagnetic transient simulation program to set up the computation model of optimization aim function and optimized algorithm, and carry out initialization;

Step 32, by described computation model, provided one group of given control parameter of current limiting low-voltage, according to described given control parameter, the electromagnetic transient simulation that carries out electric network calculates, and obtains initial optimization target function value f ₁;

Step 33, employing optimized algorithm successively produce new control parameter, again carry out electromagnetic transient simulation calculating, obtain optimization aim function calculated value f _j, when:

$\left\{\begin{array}{c}|f_j-f_{j-1}|\&le;\mathrm{\&epsiv;}\\ f_j<\min \left\{f_i\right\}\\ i\&Element;(0,j),i\&Element;Z\end{array}\right.---\left(2\right)$

Time, think and calculate convergence, this optimization aim function calculated value f _jcorresponding control parameter is optimal control parameter, otherwise, execution step 34;

Step 34, judgement are optimized number of times and whether are reached maximum simulation times, if so, choose optimization aim function calculated value f _jwith initial optimization target function value f ₁a corresponding control parameter of middle minimum is as optimal control parameter, otherwise continuation performs step 33.

2. the optimization method of low voltage limit flow control parameter according to claim 1, is characterized in that, Δ E in described step 1 _losscomputational methods be:

$\left\{\begin{array}{c}{\mathrm{\&Delta;E}}_{\mathrm{loss}}=E_{\mathrm{loss}}/E_{\mathrm{loss}0}-1.0\\ E_{\mathrm{loss}}={\&Integral;}_{t0}^{t1}(P_s-P\left(t\right))\mathrm{dt}\\ E_{\mathrm{loss}0}={\&Integral;}_{t0}^{t1}(P_s-P_0\left(t\right))\mathrm{dt}\end{array}\right.---\left(3\right)$

Wherein, P _sfor the active power that direct current under steady state situations is carried, P ₀be respectively under same fault condition with P, direct current system adopts low voltage limit flow control parameter initial value and optimal control parameter to calculate separately the active power of gained, and t0 is the fault clearance moment, and t1 is that direct current active power returns to P _smoment of 90%.

3. the optimization method of low voltage limit flow control parameter according to claim 2, is characterized in that, described Δ Q _peakcomputational methods be:

ΔQ _peak＝Q _peak/Q _peak0-1.0(4)

Wherein, Q _peak0and Q _peakbe respectively under same fault condition, direct current system adopts low voltage limit flow control parameter initial value and optimal control parameter to calculate separately the idle numerical value of maximum that between convalescence of gained, inverter consumes.

4. according to the optimization method of the low voltage limit flow control parameter described in claim 2 or 3, it is characterized in that, the current limiting low-voltage of described low voltage limit flow control parameter initial value when not being optimized controlled parameter value.

5. according to the optimization method of the low voltage limit flow control parameter described in claim 2 or 3, it is characterized in that, according to engineering experience, the number range of described three variablees limited:

$\left\{\begin{array}{c}0.4\&le;\mathrm{VD}\_H\&le;0.9\\ 0.1\&le;\mathrm{VD}\_L\&le;0.6\\ 0.2\&le;\mathrm{ID}\_L\&le;0.5\\ \mathrm{VD}\_H\&GreaterEqual;\mathrm{VD}\_L\end{array}\right.---\left(5\right).$

6. according to the optimization method of the low voltage limit flow control parameter described in claim 2 or 3, it is characterized in that, it also further comprises step 4, by electromagnetic transient simulation, contrasts the dynamic response under low voltage limit flow control parameter initial value and optimal control parameter, the feasibility of checking optimum results.

7. the optimization method of low voltage limit flow control parameter according to claim 6, is characterized in that, described dynamic response comprises the active power of inverter transmission and the reactive power of consumption.

8. the optimization method of low voltage limit flow control parameter according to claim 1, is characterized in that, described optimized algorithm is genetic algorithm.